I have watched so many documentaries about decoding but I didn’t understand very well. What I know is move the letters of the word to the front of the alphabet and then move by 1 each time. Example with the word ‘coin’
C O I N A B D E F G H J K L M P Q R S T U V W X Y Z
O I N A B D E F G H J K L M P Q R S T U V W X Y Z C
I N A B D E F G H J K L M P Q R S T U V W X Y Z C O
… and so on so forth but how do they know which letter is which.
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In your example the word to encode is “coin”
To encode it we will use the simple “move by 1” method, also called a “cypher”
C becomes D
O > P
I > L
N > M
the **encoded** word is DPLM, also called cyphertext.
Reverse the process (subtract a letter) to **decode**.
We can add values for different letters , so a C could shift 3 letters, and a N shift 1 or 0,
Ben Eater has a video about deciding the PS/2 keyboard. This can help you understand how older keyboards worked. The USB HID interface is different but the ideas would be similar.
Encoding and decoding are generally not cyphers or encryption. They are a way to use one algorithm to change one thing to another format.
For example, a common way to send images and other data files over the Internet is Base64. There’s a group of 64 characters(A-Z,a-z,0-9,+,/, plus = for padding), each mapped to a combination of 6 bits (6 bits = 2 to the power of 6 = 64 possible combinations). So the first six bits of your file are read and assigned the appropriate character. This continues until your file is done and you have a string of characters. Since they are characters, they can be sent over text-based systems such as email, and the old news groups.
Then at the other end, your program reads a character and puts out the correct 6 bits, doing this until all characters are read. Now you have your image file back, it’s been decoded.
That’s encoding/decoding. If you have some kind of a key that is required to encode, and that key is needed to decode, then you have a cypher, or encryption.
The lines can get a little blurred. Say you have to input a 6-bit key into Base64 so that in the process of encoding it scrambles each 6 bits with your key (say a bitwise XOR). Then decoding will produce gibberish unless you have the key, since the bits weren’t flipped back. It’s not very good encryption if you know how it was encrypted since there are only 64 possible keys. But it’s still encryption with a key.
So an encoding where nobody knows how it’s been done can be used to keep people from seeing the data, so it’s almost encryption. The problem is that when your encoding algorithm is realized, then all messages you sent using that encoding are readable. It’s just like Base64 now.
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